1、 Reference number ISO/TR 12134:2010(E) ISO 2010TECHNICAL REPORT ISO/TR 12134 First edition 2010-02-15 Rubber Estimation of uncertainty for test methods Non-functional parameters Caoutchouc Estimation de lincertitude des mthodes dessai Paramtres non fonctionnels ISO/TR 12134:2010(E) PDF disclaimer Th
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6、y in the country of the requester. ISO copyright office Case postale 56 CH-1211 Geneva 20 Tel. + 41 22 749 01 11 Fax + 41 22 749 09 47 E-mail copyrightiso.org Web www.iso.org Published in Switzerland ii ISO 2010 All rights reservedISO/TR 12134:2010(E) ISO 2010 All rights reserved iiiContents Page Fo
7、reword iv Introduction.v 1 Scope1 2 Summary of preparing an uncertainty budget .1 3 The elements of the uncertainty budget .2 4 Selected test methods and sources of uncertainty.3 4.1 General .3 4.2 Density3 4.3 Tensile strength (or modulus)4 4.4 Elongation at break .4 4.5 Tear strength4 4.6 Compress
8、ion set .4 4.7 Hardness 5 4.8 Heat ageing 5 4.9 Effect of liquids (volume swell)5 4.10 Abrasion resistance 6 4.11 Gehman low-temperature stiffness .6 4.12 Impact brittleness6 4.13 Temperature of retraction test .6 4.14 Ozone resistance.7 4.15 Stress relaxation7 5 Methods of deriving uncertainty esti
9、mates for non-functional parameters7 5.1 Empirical evaluation7 5.2 Calculation .8 5.3 Expert opinion .8 5.4 Interlaboratory testing 8 Bibliography9 ISO/TR 12134:2010(E) iv ISO 2010 All rights reservedForeword ISO (the International Organization for Standardization) is a worldwide federation of natio
10、nal standards bodies (ISO member bodies). The work of preparing International Standards is normally carried out through ISO technical committees. Each member body interested in a subject for which a technical committee has been established has the right to be represented on that committee. Internati
11、onal organizations, governmental and non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization. International Standards are drafted in accordance with the rul
12、es given in the ISO/IEC Directives, Part 2. The main task of technical committees is to prepare International Standards. Draft International Standards adopted by the technical committees are circulated to the member bodies for voting. Publication as an International Standard requires approval by at
13、least 75 % of the member bodies casting a vote. In exceptional circumstances, when a technical committee has collected data of a different kind from that which is normally published as an International Standard (“state of the art”, for example), it may decide by a simple majority vote of its partici
14、pating members to publish a Technical Report. A Technical Report is entirely informative in nature and does not have to be reviewed until the data it provides are considered to be no longer valid or useful. Attention is drawn to the possibility that some of the elements of this document may be the s
15、ubject of patent rights. ISO shall not be held responsible for identifying any or all such patent rights. ISO/TR 12134 was prepared by Technical Committee ISO/TC 45, Rubber and rubber products, Subcommittee SC 2, Testing and analysis. ISO/TR 12134:2010(E) ISO 2010 All rights reserved vIntroduction I
16、t is now a requirement that laboratories accredited to ISO/IEC 17025 2take into account the measurement or calibration uncertainties associated with any work they have performed when assessing conformity of the material or product to a given specification. As there is an increasing requirement for t
17、raceability of measurement, more and more technical staff find themselves faced with the task of carrying out an uncertainty evaluation on their reported measurement results. Currently, the primary source document for guidance on measurement uncertainty is ISO/IEC Guide 98-3 1 , to which the interes
18、ted reader is referred for details. Eurolab Technical Report No. 1/2007 5is a very useful guide to alternative approaches to uncertainty evaluation, whilst ISO/TS 21748 3gives guidance on the use of repeatability/reproducibility data for uncertainty estimation. TECHNICAL REPORT ISO/TR 12134:2010(E)
19、ISO 2010 All rights reserved PROOF/PREUVE 1Rubber Estimation of uncertainty for test methods Non-functional parameters 1 Scope This Technical Report provides guidance to scientists, engineers and technicians, working in the field of rubber materials and products, to supplement ISO/IEC Guide 98-3 and
20、 to provide additional guidance in situations where functional relationships between input quantities (such as temperature, strain rate and time) and derived output quantities (such as tensile strength and compression set) are unknown and where no other guidance is available. This Technical Report p
21、rovides a summary of the classical approach that is taken in the preparation of uncertainty budgets and provides in Clause 4 a list of selected test methods and, for each, an indication of the factors that will make a contribution to the uncertainty budget. Clause 5 discusses how “non-functional” fa
22、ctors can be taken into account in the classical approach. 2 Summary of preparing an uncertainty budget The analysis of most measurement uncertainties can be reduced to a step-by-step procedure. This procedure comprises the following steps: a) define the functional relationship between the input mea
23、surements and the measurand (the quantity being measured, e.g. tensile strength); b) compile a list of all the factors that are expected to contribute to the uncertainty in the measurand; c) for each of the uncertainty sources, estimate the magnitude of the uncertainty; d) from the relationship defi
24、ned in step a), estimate the effect that each functional quantity has on the measurement result, using direct mathematical techniques; e) for the non-functional quantities, estimate their effect through other sources, such as secondary experimentation or expert opinion; f) combine the uncertainties
25、in all the input quantities to obtain the uncertainty in the output quantity; g) express the expanded uncertainty as an interval about the measurement result within which it is anticipated, with a stated level of confidence, that the measurand will lie. ISO/TR 12134:2010(E) 2 ISO 2010 All rights res
26、erved3 The elements of the uncertainty budget Taking each of the seven steps in turn: a) The functional relationship between the measurand and its input variables is given in the International Standard for the test method being examined. For example, the functional relationship for tensile strength,
27、 , is given by: F wt = where F is the force at break; w is the test piece width; t the test piece thickness. b) See Clause 4 for listings of factors that can be expected to have some influence on the result of the test. c) Estimating the magnitude of the uncertainty, u(x), is often the most difficul
28、t part in preparing the uncertainty budget. Two main types are identified in ISO/IEC Guide 98-3. Type A uncertainties relate to random effects. Typically, the type A evaluation will be applied to the material property data that has been determined by the test method, e.g. the tensile strength, compr
29、ession set or volume swell. Such data will generally be normally distributed about their mean (or sufficiently close to a normal distribution for the deviation to be insignificant) so that an estimate of the standard uncertainty can be deduced by means of the usual statistical procedures. The standa
30、rd uncertainty is given by the standard error of the mean. The second, type B, relates to systematic effects and is applied to the analysis of such parameters as the calibration of an instrument or the drift between calibrations. Such sources of uncertainty should be evaluated on the basis of the in
31、formation available, such as a calibration certificate, the manufacturers specifications or professional judgement and past experience. Part of that experience is in deciding what kind of distribution the uncertainty will take. Often this is not a normal distribution, and rectangular or sometimes tr
32、iangular distributions are often encountered. Reference should be made to ISO/IEC Guide 98-3 for further details, but in all cases the standard uncertainty is given by the standard deviation of the distribution that has been chosen. d) Once the standard uncertainty for each of the functional factors
33、 has been estimated, the sensitivity coefficient for each must be found. This is the first derivative of the measurand with respect to the parameter being considered. Thus, for tensile strength, the sensitivity coefficient, c, for the force is simply: 1 F c F wt = while for the width it is: 2 w F c
34、w wt = An alternative to formal differentiation is to add a small increment to the factor (for example, add w to w), calculate the new value for the tensile strength (call this +), then subtract this same increment, w, from w and recalculate tensile strength (call this ). Then determine the sensitiv
35、ity coefficient from the expression: ()() 2 w c w + = ISO/TR 12134:2010(E) ISO 2010 All rights reserved 3Having found the sensitivity coefficient, the contribution that the factor makes to the uncertainty of the measurand is simply the product of its standard uncertainty and its sensitivity coeffici
36、ent. e) Those factors that have an influence on the measurand but which do not contribute to the functional relationship given in step a) above similarly need to be quantified. This aspect of deriving the uncertainty budget is not explicitly covered by ISO/IEC Guide 98-3 or other documents, and yet
37、typically there are many more of these “non-functional” parameters in rubber testing than there are functional ones. Suggestions as to how these may be taken into account are given in Clause 5 of this Technical Report. f) The combined standard uncertainty of all the individual factor uncertainties q
38、uantified in steps d) and e) above are combined by means of a root mean square process. Taking just the three functional parameters for tensile strength by way of illustration: 222 () () () () F wt uu F cu w cu t c =+ g) This combined standard uncertainty is the equivalent of one standard deviation
39、of a normal distribution function. It is conventional, however, for us to work at a confidence level of 95 %, and so this combined standard uncertainty needs to be multiplied by a coverage factor, k, in order to increase the probability that the true value of the property we are considering lies wit
40、hin the expanded combined uncertainty of our measured value more specifically, that this will happen 95 % of the time. It is conventional to take the coverage factor as being 2. Thus: ()2() Uu = The end result of this process is to enable the test result we have obtained to be quoted with an associa
41、ted level of uncertainty at a given level of confidence. Thus an uncertainty statement would be of the form: The tensile strength of compound X was (Z U) MPa, with an estimated uncertainty of 95 %. 4 Selected test methods and sources of uncertainty 4.1 General In all cases, the uncertainty arising f
42、rom material variability will be evaluated using the type A method of calculation. In addition to the non-functional parameters listed below, almost every test method is subject to uncertainties due to the temperature and humidity of test. It is generally assumed that, if the temperature is within t
43、he relevant tolerance given in ISO 23529 4 , the associated uncertainty is negligible. Humidity is only considered significant for electrical tests. Similarly, for many test methods the quality of the cutting out of test pieces could influence the result. It is generally assumed that, for standard t
44、est pieces, if the cutting process and the quality of the cutter conform to ISO 23529, the associated uncertainty can be neglected. 4.2 Density Functional parameters Accuracy of balance (at least two weighings) Non-functional parameters Immersion-liquid density at test temperature (this can be calcu
45、lated) Test temperature Absorption of liquid by test material Effect of suspension thread (this can be calculated) Air bubbles adhering to material surface (this will be an inseparable part of the between-test-piece variability) ISO/TR 12134:2010(E) 4 ISO 2010 All rights reserved4.3 Tensile strength
46、 (or modulus) Functional parameters Force measurement Test piece width Test piece thickness Non-functional parameters Test speed Alignment of test piece (this will be an inseparable part of the between- test-piece variability) 4.4 Elongation at break Functional parameters Initial gauge length Extens
47、ometer accuracy Non-functional parameters Test speed Alignment of test piece (this will be an inseparable part of the between- test-piece variability) 4.5 Tear strength Functional parameters Force measurement Test piece thickness Non-functional parameters Test speed Depth of nick (some methods) Accu
48、racy of angle (angle tear) Alignment of test piece (this will be an inseparable part of the between-test-piece variability) 4.6 Compression set Functional parameters Initial thickness of test piece Final thickness of test piece Spacer thickness Non-functional parameters Ageing temperature Test durat
49、ion Recovery time Slippage of, or adhesion between, test piece and metal compression plate (these will be an inseparable part of the between-test-piece variability) ISO/TR 12134:2010(E) ISO 2010 All rights reserved 54.7 Hardness Non-functional parameters Indentor dimensions (including angles for Shore durometers) Dial accuracy Parallax errors in reading dial Load or spring forces For durometers, the force applied to the foot Time of force application Friction in meter Hardness is unusu
